In HIV-infected patients treated with HAART, there are variable rates of reconstitution of T cell numbers and function. An understanding of the mechanisms underlying the recovery of T cells will be important for the design of future strategies to improve T cell reconstitution. The thymus is the organ responsible for producing new naive T cells with a broad immune repertoire from bone marrow-derived precursors. IL-7 is a cytokine that has direct effects upon the thymus and naive T cells. This study examines the role of the thymus in HIV infection and immune reconstitution, and how IL-7 can affect that role.This study seeks to improve our understanding of how HAART affects the immune response to HIV, and how therapeutic vaccination, with or without additional interventions, will lead to improved immunity against HIV and better control of virus replication.